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R&S C4 : Routing Concepts (4.4 Summary ( (cisco routers and cisco…

cisco routers and cisco switches have many similarities. They support a similar model operating system, similar command structures , and many of the same commands

one distinguishing feature between switches and routers is the type of interfaces supported by each

the main purpose of a router is to connect multiple networks and forward pacckets from one network to the next. This means that a router typically has multiple interfaces. Each interface is a member or hos on a different IP network

there are many key structures and performance-related characteristics referred to when discussing networks: topology, speed, cost, security, availability, scalability, and reliability

a remote network is a network that can only be reached by forwarding the packet to another router

remote networks are added to the routing table in two ways

by network administrator manually

implementing a dynamic routing protocol

static routes do not have as much overhead as dynamic routing protocolshowever, static routes can require more maintenance if the topology is constantly changing or is unstable

routers make their primary forwarding decision at Layer 3, the Network layer.However, router interfaces participate in Layers 1,2 and 3.Layer 3 IP packets are encapsulaed into a Layer 2 data link frame and encoded into bits at Layer 1

router interfaces participate in Layer 2 processes associated with their encapsulation. For example, an Ethernet interface on a router participates in the ARP process like other hosts on that LAN

Components of the IPv6 routing table are very similar to the IPv4 routing table

4.1 Initial Configuration of a Router

4.1.1 Functions of a Router

4.1.1.1 Characteristics of a Network

Topology

Speed

Cost

Security

Availability

Scalability

Reliabillity

4.1.1.2 Why Routing ?

connect one network to another

4.1.1.3 Routers Are Computers

CPU

OS

Memory and storage

Routers store data using:

Random Access Memory (RAM)

Volatile

(vluchtig / vervliegend)

Running IOS

Running configuration file

IP routing and ARP tables

Packet buffer

Read-Only Memory (ROM)

Non-Volatile

bootup instructions

basic diagnostic software

limited IOS

Non-Volatile Random Access Memory (NVRAM)

non-volatile

startup configuration file

Flash

non-volatile

IOS

Other system files

4.1.1.4 Routers Interconnect Networks

4.1.1.5 Routers Choose Best Paths

determine the best path to send packets

forward packets toward their destination

(PPP) - Point-to-Point protocol

use routing tables to send packets

use static routes and dynamic roting protocols to learn about remote networks and build their routing tables

4.1.1.6 Packet Forwarding Mechanisms

Process switching

CPU matches destination address with entry in its routing table

Fast switching

fast switching cache to store next-hop information

Cisco Express Forwarding (CEF)

table entries are not packet-triggered like fast switching bu tchange-triggered

4.1.1.7 Activity - Identify Router Components

4.1.1.8 - 4.1.1.9 PT + Lab

4.1.2 Connect Devices

4.1.2.1 Connect to a Network

4.1.2.2 Default Gateways

IP address

Subnet mask

identifies with which networksubnet the host can communicate

Default gateway

identifies the router to send apacket to when the destination is not on the same local network subnet